Space heater having a heating air flow duct with a heat exchanger for engine cooling water and one for combustion gases

ABSTRACT

A space heater particularly for automobiles comprises a heating air flow passage in which is positioned a heat exchanger which is supplied with water from an engine cooling system and a second heat exchanger which is supplied with combustion gases from a separately operated fuel burner.

United States Patent 1 Kofink 1 1 Dec. 11, 1973 1 SPACE HEATER HAVING A HEATING AIR FLOW DUCT WITH A HEAT EXCHANGER FOR ENGINE COOLING WATER AND ONE FOR COMBUSTION GASES [75] Inventor: Siegfried Kofink, Lenzhalde,

Germany [73] Assignee: .1. Eberspacher, Esslinger, Germany [22] Filed: Nov. 23, 1971 [21] Appl. No.: 201,352

[30] Foreign Application Priority Data I Mar. 3, 1971 Germany P 21 10 182.6

[52] US. Cl. 237/l2.3 A, 237/123 B, 237/123 C,

432/223 [51] Int. Cl B60h 1/02 [58] Field of Search 237/123 B, 12.3 C,

[56] References Cited UNITED STATES PATENTS 3,401,920 9/1968 Berkhoudt et a1. 263/19 A R26,599 6/1969 Fairbanks et a1. 237/123 R Primary ExaminerMeyer Perlin Assistant ExaminerR. Capossela Att0rney.10hn J. McGlew et a1.

[57] ABSTRACT A space heater particularly for automobiles comprisesa heating air flow passage in which is positioned a heat exchanger which is supplied with water from an engine cooling system and a second heat exchanger which is supplied with combustion gases from a separately operated fuel burner.

13 Claims, 4 Drawing Figures Pmmwnm n mm 3377375 SHEET 2 OF 2 SPACE HEATER HAVING A HEATING AIR FLOW DUCT WITH A HEAT EXCHANGER FOR ENGINE COOLING WATER AND ONE FOR COMBUSTION GASES BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates in general to the construction of space heaters and in particular to a new and useful space heater particularly for an automobile which includes a heating air flow duct in which is located a first heat exchanger for the air circulated which is operated by the combustion engine cooling liquid system and a second heat exchanger which is operated from combustion gases produced in a separate fuel burner.

2. DESCRIPTION OF THE PRIOR ART The invention relates to the construction of a space heater for motor vehicles which include a water-cooled engine and in which the liquid of the water cooling system is employed for heating the space heating air along with an auxiliary heating system. In the known system of this type an entire auxiliary heater including the combustion system which operates from the fuel or gasoline is arranged in a ram air shaft of the main heater which utilizes the engine heat and which forms the heating air duct. Such an arrangement is possible, however, only with very large heating air ducts and it has the disadvantage that high temperatures are developed in the heating air duct since only a relatively small heating fluid capacity is available in view of the limited space and the combustion part must therefore work with a high operating temperature. The resulting high temperature can lead to thermal deformations of the duct structure and destruction or even ignition of the plastic parts which are included on such structures. Such a condition has the added disadvantage that it is accompanied by considerable annoying odor.

It is known to install in the heating water circuit of a water cooled engine an auxiliary water heat exchanger which can be heated by combustion gases of an auxiliary fuel heating burner. Such a known arrangement is relatively slow in its operation as an auxiliary heater since in addition to heating the vehicle the water circuit must be also heated and this is not necessary when the automobile is parked. Nevertheless, the auxiliary heater heats the entire vehicle through the water circuit and this indirect method is therefore associated with unnecessary fuel consumption.

Both the known auxiliary heating systems have the advantage, however, that they permit preheating of the cooling water circuit before the engine is started or during the first minutes of driving, for example, in city traffic, and therefore effect a faster heating of the cooling water to the optimum operating temperatures than is possible when operating with the heat of the engine alone. In the known type of auxiliary heating it is necessary to arrange the auxiliary heat exchanger upstream of the water heat exchanger whichis admitted by the cooling water. Independently thereof both known auxiliary heating systems show a functional fusion with elemerits of the mainhot water heating system which is provided in any event by the water coolingsystem of the engine and thus to this extent they reduce the total constructional cost.

SUMMARY OF THE INVENTION The present invention provides a space heating system having the advantages of the known heaters but without the disadvantages and in fact providing an additional advantage in the operation and construction of a space heater. In accordance with the invention a first heat exchanger which is adapted to be connected to the engine cooling system is arranged in the heating air flow passage along with a second heater which is connected to a separate fuel heating burner which is arranged outside of the heating duct. With the inventive construction an auxiliary heat exchanger is arranged in a duct in series with the water heat exchanger which is admitted by the engine cooling water. The auxiliary heat exchanger is supplied with thermal energy which is generated on the exterior of the heating duct by a fuel heat burner which can be arranged in the most suitable spot of the vehicle. In most cases it is possible to arrange, in the vehicle, fuel heating burners with a large volume which have a high heating fluid capacity and which are thus capable of producing the necessary heat for the auxiliary heater with a relatively low operating temperature. It is preferred, however, to usefuel heating burners with a small volume in order to keep the space requirement for the auxiliary heater in a vehicle as low as possible, and the efficiency of the fuel heating burner at an optimum value. Because of the high operating heat of the small fuel burners having combustion gas temperatures of around l,500 C., the arrangement of the invention makes the space requirement less critical because the fuel heating burner is no longer confined to a position in the heating air duct but can be arranged at any suitable point in the vehicle. In order to arrange the system so that there will be no undesirable excessive heat in the heat air duct indirectly, by a heat which is given off by the fuel burner, the feed pipe for the heating fluid or gases is designed as a mixing pipe of a first fluid which is heated by the fuel heating burner and of an unheated second fluid. This construction ensures that there will be a considerable increase in the amount of heating gases which can be fed to the auxiliary heat exchanger eventhough there is a resultant temperature reduction. A mixing ratio between the unheated first fluid and a second heated fluid or gases may be in the range of from 1 to 3 or from l to 5, for example. A temperature in the heating air duct of the main heater of from between 1l0 and C. as a lower limit and between 250 and 300 C. as an upper limit is desirable. In this temperature range any dust which waves in with the heating air does not burn and the parts which are normally used for the assembly, particularly any plastic parts, do not suffer any ill effects from the relatively low heat. In addition, it is ensured that no liquid can condense in the heating air duct on the heat exchanger and that any deposited moisture will be expelled by evaporation.

The first fluid can absorb the heat generated in the fuel heating burner indirectly over a separate heat exchanger and conduct it in a separate open or closed circuit to the auxiliary heat exchanger in the heating air duct of the main heater. If the safety rules for the vehicle concerning the conduction of the exhaust gases permit, it is preferred, however, to use as a first fluid the exhaust gases directly from the fuel burner since the inertia of the auxiliary heater is lowest and the heat losses are best avoided. In both constructions it is advisable that the second fluid flow through a line provided with a suction fan into the feed pipe of the-heating fluid. The

inlet section of the mixing pipe for the second fluid is preferably designed as an injector.

Fuel heating burners which comprise a combustion chamber with a fuel supply and means for atomizing the fuel and which include an air intake and an exhaust gas offtake, as well as an annular jacket which is traversed by atmospheric air are particularly suitable as an auxiliary heater for the invention construction. Fuel heating burners of this type are known as complete auxiliary heaters and they serve as heat exchanges for transferring the combustion heat to the heating air which flows in the annular space of the heater. In order to adapt such a fuel heating burner to the invention, the exhaust gas takeoff and the annular flow space for fresh air are combined and delivered to the auxiliary heat exchanger. With such a fuel heating burner it is possible to design the partition between the combustion chamber and an annular jacket surrounding the combustion chamber as a heat exchanger wall. A known complete auxiliary heater which includes a common inlet arranged on the longitudinal axis of the fuel heating burner for the air intake for the combustion chamber and which also includes an annular jacket surrounding the air intake which connects into the outlet connection for the gases which are generated may be used for the auxiliary heater of the invention. The exhaust gas discharge of the combustion chamber is arranged coaxially with the outlet connection and in this way the exhaust gases which comprise the first fluid can be conducted to the auxiliary heat exchange and be combined with a second fluid entering from the annular jacket surrounding the combustion chamber.

The feed of combustion air to the combustion chamber is effected preferably by connecting the combustion chamber by inlet orifices for the combustion air which are distributed around a circumference of the annular jacket.

The auxiliary heat exchanger is advantageously made oblong in the direction of the heating air duct and fills the free cross section of the heating air duct when it is of shallow depth because of the high operating heat developed there. The ram air which is admitted to the auxiliary heat exchanger is heated there to a high temperature and mixed in the heating duct itself with the cold air passing over the auxiliary heat exchanger. Super heated temperature is not produced in the heating air duct of the main heater and it is therefore provided that the auxiliary heat exchanger has substantially the same transverse dimensions as the water heat exchanger but a very small depth related to the transverse dimension.

Accordingly it is an object of the invention to provide a space heater construction particularly for automobiles which includes a heating air flow passage in which is arranged a first heat exchanger for operation with the cooling system of the combustion engine and a second heat exchanger which is operated by a separate fuel burner arranged outside of the flow passage.

A further object of the invention is to provide a space heating arrangement which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a schematic sectional view of a space heater system constructed in accordance with the invention;

FIG. 2 is a schematic longitudinal sectional view of a fuel burner used with the system of FIG. 1;

FIG. 3 is an enlarged sectional view of the auxiliary heat exchanger employed in the system of FIG. 1; and

FIG. 4 is a section taken along the line lV-IV of FIG. 3.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, in particular, the space heater system of the invention shown particularly in FIG. 1, comprises a heating air duct generally designated 1 for heating the compartment space of a motor vehicle and which includes a heat exchanger 22 which is operated by the cooling water from a combustion engine 3 of the vehicle.

In accordance with the invention the heating air duct also carries a second heat exchanger 20 which is operated from heating gases which are produced by a fuel heating burner generally designated 5.

The heating air duct 1 is designed as a ram air shaft of the motor vehicle and it has an oblong substantially rectangular form and includes a fresh air inlet 10 which has an extension, (not shown), which is arranged behind the front hood of the motor vehicle, (not shown), in front of its windshield. The inlet cross section is smaller than the interior of the heating duct itself which includes a front housing portion 12 and is made of a material which may be plastic or provided with a plastic lining if desired. The housing portion 12 carries an electric motor 14 which has a shaft 18, which carries a fresh air blower 16 designed as an axial fan. The arrows shown in FIG. 1 shows the direction of incoming air flow which passes through the fresh air inlet 10 into the heating duct 1 and over the electric motor 14. The air flow is first passed through the second heat exchanger 20 which is arranged upstream of the heat exchanger 22, and then it moves through the first heat exchanger 22 and through either a defroster duct 38 or a main compartment space duct 40.

The heat exchanger 22 is a water-air heat exchanger which is admitted by the cooling water of the engine 3 of the motor vehicle and which transfers the heat of the cooling water to the fresh air passing through the heating duct 1. The cooling water is pumped by means of a water pump 24 through a connecting duct 26 from the engine cooling water outlet 28 to the heat exchanger water inlet 30, and it flows from the heat exchanger outlet 32 back to the engine cooling water inlet 34. A shut-off cock 36 is arranged in the duct 26 between the pump 24 and the heat exchanger inlet 30.

The auxiliary heat exchanger or second heat exchanger 20 has substantially the same transverse dimensions as the heat exchanger 22 but is of a lesser depth. As seen in FIGS. 3 and 4, the heat exchanger 20 has a smaller depth compared to its transverse dimension. The fresh air passes, as indicated by the arrows in FIG. 4, through the air heating duct 1 in the depth direction through openings or passages 42 of the housing 44, and they also pass over the housing from the exterior. The auxiliary heat exchanger is a gas air heat exchanger which is heated by a gaseous heating fluid and which gives off its heat to the fresh air going through the air heating duct 1. As shown in FIG. 3, the gaseous heating fluid enters on a narrow side through an inlet connection 46 into the auxiliary heat exchanger and branches into several ducts 48 arranged on half the cross section of the heater and it combines again in a collecting chamber 50 at the other end of the heat exchanger. The gas then flows in a counter flow direction through ducts 52 at the other half of the cross section back to the common outlet connection 54 which is arranged on the same narrow side of the auxiliary heat exchanger 20 as the inlet connection 46. The ducts 48 extend in one direction and the return ducts 52 can also be arranged alternately in order to ensure that the temperature distribution over the flow cross section for the fresh air can be made more homogeneous. The circuit of the heating fluid through the auxiliary heat exchanger 20 is indicated by the arrows shown in FIG. 3.

As shown in FIG. 1 the inlet connection 46 of the heat exchanger is connected to the feed pipe 60 for the heating fluid. The outlet connection 54 is connected to the exhaust gas offtake or discharge 62 which is also shown in FIG. 1. This conducts the exhaust gases of the heating fluid of the auxiliary heater from the heat exchanger 20 in the direction of the arrows and from the motor vehicle to the exterior.

The feed pipe 60 is also connected to the outlet connection 72 of the fuel heating burner 5, which is shown in detail in FIG. 2.

The fuel heating burner 5 has a cartridge-type oblong housing 74 with one end which terminates in the tapered outlet connection 72 and which has another end which tapers toward an air inlet connection 76. Atmospheric air is taken in through the inlet connection by means of a radial blower 78 which is arranged directly behind the inlet opening and which is in the form of a wheel secured on the shaft 80 of an electric motor 82. The motor 82 is mounted on a ring 84 in an inner wall 86 of the fuel heating burner 5 The inner wall 86 and the outer housing 74 are both cylindrical and form an annular jacket or space 88 for the passage of the air which is directed inwardly by the blower 78' as indicated by the arrows. The end face 90 opposite to the air inlet connection forms one end wall of the interior combusition chamber part and is connected to the end of the inner wall 86. The motor 82 includes a second shaft or an extension 92 at its opposite end which carries a combustion air blower 94 which acts as a radial blower to discharge the combustion air into the combustion chamber 96. The combustion air is fed to the combustion chamber 96 through inlet openings 98 distributed around the circumference of the inner wall 86'. The combustion air moves through a diaphragm 100 secured to the inner wall 86 and extends radially to the inside through the blower 94 and through a second diaphragm 102 into the combustion chamber 96. Fuel is fed radially through a connection 104 to a fuel injector 106 and is ignited by a spark plug 108. The combustion chamber 96 leads outwardly through a discharge 110 centrally into a passage formed in the outlet 72. The fresh air which is directed along the annular space 88 joins the flow of the combusiton gases downstream of the discharge opening 110, so that this portion of the discharge outlet 72 forms a mixing chamber. This mixing chamber could be designed as an injector chamber instead of a chamber in which the annular flow mixes with the axial flow.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A space heater particularly for automobiles, comprising means defining a space heating air flow passage, a first heat exchanger arranged in said flow passage for heating the air flowing through said passage, a combustion engine liquid cooling system connected to said first heat exchanger for supplying engine cooling liquid thereto, means for directing air through said air flow passage, a second heat exchanger in said air flow passage for heating the air flowing therethrough, and a fuel operated heating burner for generating heating gases located outside of said air flow passage and connected to said second heat exchanger for supplying heating gases thereto.

2. A space heater according to claim 1, wherein said second heat exchanger comprises a shallow depth relatively wide heat exchanger filling said heating air flow passage, said heat exchanger including a partial section defining an inlet flow passage on one side connected to said heating burner for the passage of heating gases therethrough, and a partial passage on the other side joining the end of the first passage for return flow in an opposite direction, said heat exchanger having through passages for the passage of air to be heated therethrough in said air flow passage.

3. A space heater according to claim 1, wherein said fuel heating burner comprises an outer housing, an inner housing spaced inwardly from said outer housing, said outer housing having an inlet opening at one end, blower means in said outer housing for pulling combustion air into said housing and for directing it around the annular space between said inner and outer housing, said inner housing having an opening therethrough intermediate its length leading to a combustion chamber therein and having a discharge at the opposite end of said outer housing, a portion of the combustion air moving through the opening of said inner housing into said combustion chamber, and said outer housing having a discharge for said combustion gases and heating air, means for introducing fuel into said combustion chamber and for igniting the fuel therein to generate gaseous products of combustion which move out through said discharge, the heating air moving around said inner housing into mixing engagement with the combustion gases.

4. A space heater according to claim 1, wherein said second heat exchanger is arranged upstream of said first heat exchanger, blower means in said passage for directing air through said passage and through said first and second heat exchangers for discharge to a space requiring heating, and including a conduit connected between said fuel heating burner and said second heat exchanger forming a mixing conduit, said heating burner having means for directing combustion gases through said conduit and for admixing fresh air to said combustion gases.

5. A space heater according to claim 4, wherein said fresh air and said combusiton gases are mixed in the range of between 1 to 3 and l to 5.

6. A space heater according to claim 1, wherein said fuel burner includes an inner wall defining a combustion chamber and an outer wall spaced from said inner wall and defining an annular air flow space, passage means from the outer wall space into said inner wall combustion chamber, and means for igniting fuel in said combustion chamber to generate gaseous products of combustion, said outer wall joining the discharge from said combustion chamber.

7. A space heater according to claim 6, wherein said means for directing said combustion air into said combustion gases comprises an injector.

8. A fuel heating burner comprising an outer tubular casing and inner tubular casing spaced from said outer tubular casing and defining a combustion chamber with a discharge opening into said outer tubular casing, said outer tubular casing having a discharge downstream of said inner tubular casing discharge opening and having an opposite end with an inlet opening, said inner tubular housing having an opening intermediate its length, means for directing combustion air inwardly to the inlet opening of said outer housing arid around said inner wall and through the opening thereof into said combustion chamber with a portion being directed between said inner housing and outer housing to said outer housing discharge.

9. A fuel heating burner according to claim 8, including a feed pipe for the combustion gases and the heating fluid connected to said outer housing discharge.

10. A fuel heating burner according to claim 8, wherein said inlet is arranged along the longitudinal axis of said heating burner, said inner housing opening at the opposite end in a discharge along said longitudinal axis coaxial to the outlet of said outer housing.

11. A fuel heating burner according to claim 8, wherein said combustion chamber is connected to the space between said inner and outer housings by inlet orifices distributed around its circumference.

12. A fuel heating burner according to claim 8, wherein said first heat exchanger has substantially the same transverse dimensions as said second heat exchanger, said second heat exchanger having a smaller depth than said first heat exchanger and a smaller depth than its transverse dimension.

13. A space heater particularly for automobiles, comprising a housing defining a space heating air flow passage, a first heat exchanger arranged in said flow passage for heating the air flowing through said passage, a combustion engine liquid cooling system connected to said first heat exchanger for supplying engine cooling liquid thereto to transfer the heat of the cooling liquid to the air flowing through said passage, a second heat exchanger in said air flow passage upstream of said first heat exchanger for heating the air flowing therethrough and through said first heat exchanger for heating the engine cooling liquid supplied thereto as required, a fuel operated heating burner for generating heating gases located outside of said air flow passage and connected to said second heat exchanger for supplying heating gases thereto, and blower means associated with said passage for directing air through said passage and through said first and second heat exchangers for discharge to a space requiring heating. 

1. A space heater particularly for automobiles, comprising means defining a space heating air flow passage, a first heat exchanger arranged in said flow passage for heating the air flowing through said passage, a combustion engine liquid cooling system connected to said first heat exchanger for supplying engine cooling liquid thereto, means for directing air through said air flow passage, a second heat exchanger in said air flow passage for heating the air flowing therethrough, and a fuel operated heating burner for generating heating gases located outside of said air flow passage and connected to said second heat exchanger for supplying heating gases thereto.
 2. A space heater according to claim 1, wherein said second heat exchanger comprises a shallow depth relatively wide heat exchanger filling said heating air flow passage, said heat exchanger including a partial section defining an inlet flow passage on one side connected to said heating burner for the passage of heating gases therethrough, and a partial passage on the other side joining the end of the first passage for return flow in an opposite direction, said heat exchanger having through passages for the passage of air to be heated therethrough in said air flow passage.
 3. A space heater according to claim 1, wherein said fuel heating burner comprises an outer housing, an inner housing spaced inwardly from said outer housing, said outer housing having an inlet opening at one end, blower meanS in said outer housing for pulling combustion air into said housing and for directing it around the annular space between said inner and outer housing, said inner housing having an opening therethrough intermediate its length leading to a combustion chamber therein and having a discharge at the opposite end of said outer housing, a portion of the combustion air moving through the opening of said inner housing into said combustion chamber, and said outer housing having a discharge for said combustion gases and heating air, means for introducing fuel into said combustion chamber and for igniting the fuel therein to generate gaseous products of combustion which move out through said discharge, the heating air moving around said inner housing into mixing engagement with the combustion gases.
 4. A space heater according to claim 1, wherein said second heat exchanger is arranged upstream of said first heat exchanger, blower means in said passage for directing air through said passage and through said first and second heat exchangers for discharge to a space requiring heating, and including a conduit connected between said fuel heating burner and said second heat exchanger forming a mixing conduit, said heating burner having means for directing combustion gases through said conduit and for admixing fresh air to said combustion gases.
 5. A space heater according to claim 4, wherein said fresh air and said combusiton gases are mixed in the range of between 1 to 3 and 1 to
 5. 6. A space heater according to claim 1, wherein said fuel burner includes an inner wall defining a combustion chamber and an outer wall spaced from said inner wall and defining an annular air flow space, passage means from the outer wall space into said inner wall combustion chamber, and means for igniting fuel in said combustion chamber to generate gaseous products of combustion, said outer wall joining the discharge from said combustion chamber.
 7. A space heater according to claim 6, wherein said means for directing said combustion air into said combustion gases comprises an injector.
 8. A fuel heating burner comprising an outer tubular casing and inner tubular casing spaced from said outer tubular casing and defining a combustion chamber with a discharge opening into said outer tubular casing, said outer tubular casing having a discharge downstream of said inner tubular casing discharge opening and having an opposite end with an inlet opening, said inner tubular housing having an opening intermediate its length, means for directing combustion air inwardly to the inlet opening of said outer housing and around said inner wall and through the opening thereof into said combustion chamber with a portion being directed between said inner housing and outer housing to said outer housing discharge.
 9. A fuel heating burner according to claim 8, including a feed pipe for the combustion gases and the heating fluid connected to said outer housing discharge.
 10. A fuel heating burner according to claim 8, wherein said inlet is arranged along the longitudinal axis of said heating burner, said inner housing opening at the opposite end in a discharge along said longitudinal axis coaxial to the outlet of said outer housing.
 11. A fuel heating burner according to claim 8, wherein said combustion chamber is connected to the space between said inner and outer housings by inlet orifices distributed around its circumference.
 12. A fuel heating burner according to claim 8, wherein said first heat exchanger has substantially the same transverse dimensions as said second heat exchanger, said second heat exchanger having a smaller depth than said first heat exchanger and a smaller depth than its transverse dimension.
 13. A space heater particularly for automobiles, comprising a housing defining a space heating air flow passage, a first heat exchanger arranged in said flow passage for heating the air flowing through said passage, a combustion engine liquid cooling system connected to said fiRst heat exchanger for supplying engine cooling liquid thereto to transfer the heat of the cooling liquid to the air flowing through said passage, a second heat exchanger in said air flow passage upstream of said first heat exchanger for heating the air flowing therethrough and through said first heat exchanger for heating the engine cooling liquid supplied thereto as required, a fuel operated heating burner for generating heating gases located outside of said air flow passage and connected to said second heat exchanger for supplying heating gases thereto, and blower means associated with said passage for directing air through said passage and through said first and second heat exchangers for discharge to a space requiring heating. 